Although the molecular basis for obesity is largely unknown, the identification of the “OB gene” and protein encoded (“OB protein”) has shed some light on mechanisms the body uses to regulate body fat deposition. Zhang et al., Nature 372: 425-432 (1994); see also, the Correction at Nature 374: 479 (1995). The OB protein is active in vivo in both ob/ob mutant mice (mice obese due to a defect in the production of the OB gene product) as well as in normal, wild type mice. The biological activity manifests itself in, among other things, weight loss. See generally, Barinaga, “Obese” Protein Slims Mice, Science 269: 475-476 (1995).
The other biological effects of OB protein are not well characterized. It is known, for instance, that in ob/ob mutant mice, administration of OB protein results in a decrease in serum insulin levels, and serum glucose levels. It is also known that administration of OB protein results in a decrease in body fat. This was observed in both ob/ob mutant mice, as well as non-obese normal mice. Pelleymounter et al., Science 269: 540-543 (1995); Halaas et al., Science 269: 543-546 (1995). See also, Campfield et al., Science 269: 546-549 (1995) (Peripheral and central administration of microgram doses of OB protein reduced food intake and body weight of ob/ob and diet-induced obese mice but not in db/db obese mice.) In none of these reports have toxicities been observed, even at the highest doses.
The elucidation of other biological effects of the OB protein, particularly on animals which may not benefit from or may not need weight reduction, will provide additional uses for the OB protein.
One such use, as provided by the present invention, is in the increase in lean tissue mass.
Of course, modulation of diet and exercise is one way to increase muscle size. There are also compositions used to increase lean mass. Current compositions thought to increase lean tissue mass include anabolic steroids, such as testosterone and derivatives, and human growth hormone. These are noted to have undesirable side effects however. (The summary below is fully explained in Remington's Pharmaceutical Sciences, 18th Ed. (1990, Mack Publishing Co., Easton, Pa. 18042) Chapter 50, at pages 948-1001.))
Human growth hormone, such as Protropin and Somatropin are noted to frequently cause hypercalciuria, which usually regresses in 2 to 3 months. Hyperglycemia and frank diabetes mellitus are also noted to occur. Myalgia and early morning headaches are noted to be relatively frequent, and occasionally cases of hypothyroidism and supersaturation of cholesterol in bile may occur. If the epiphyses are closed, the hormone should not be used because continued stimulation of growth of the phalanges and jawbone, but not other bones, can cause abnormal body proportions.
Anabolic steroids increase athletic performance and aggressiveness. Their use has been condemned by the American College of Sports Medicine. Female performance is improved, but at the expense of virilization and acne vulgaris. Androgens cause hirsutism, deepening or hoarseness of the voice, precocious puberty and epiphyseal closure in immature males, increased libido (in both male and female) priapism, oligospermia, and testicular atrophy, enlargement of the clitoris in the female, flushing, decreased ejaculatory volume and sperm population, gynecomastia, hypersensitivity, acne, weight gain, edema and hypercalcemia. Prolonged use increases aggressiveness, sometimes enormously, and many assaults are stated to be attributable to androgen abuse. Paranoia-like and other psychotic behavior has been reported. Biliary stasis and jaundice occur. There have been a few cases reported of hepatoma following long term therapy.
It is therefore desirable to have a therapeutic or cosmetic composition which increases lean tissue mass without side effects seen in the presently available drugs.